You do the implcit differentation, then solve for y' and check where this is defined.
In your case: Differentiate implicitly: 2xy + x²y' - y² - x*2yy' = 0
Solve for y': y'(x²-2xy) +2xy - y² = 0
y' = (2xy-y²) / (x²-2xy)
Check where defined: y' is not defined if the denominator becomes zero, i.e.
x² - 2xy = 0 x(x - 2y) = 0
This has formal solutions x=0 and y=x/2. Now we check whether these values are possible for the initially given definition of y:
0^2*y - 0*y^2 =? 4 0 =? 4
This is impossible, hence the function is not defined for 0, and we can disregard this.
x^2*(x/2) - x(x/2)^2 =? 4 x^3/2 - x^3/4 = 4 x^3/4 = 4 x^3=16 x^3 = 16 x = cubicroot(16)
This is a possible value for y, so we have a point where y is defined, but not y'.
The solution to all of it is hence D - { cubicroot(16) }, where D is the domain of y (which nobody has asked for in this example :-).
(Actually, the check whether 0 is in D is superfluous: If you write as solution D - { 0, cubicroot(16) }, this is also correct - only it so happens that 0 is not in D, so the set difference cannot take it out of there ...).
If someone asks for that D, you have to solve the definition for y and find that domain - I don't know of any [general] way to find the domain without solving for the explicit function).
1) set up a problem
you know you want to get an avg of 94 but how do you do avg in the first place. you add up the numbers then divde by the total number of numbers used lol
so

92.5 is the avg number for the last 3 tests
"x" is the 4th test score which we want to find out
"2" is the total number of numbers being added together
so now lets get x to one side
92.5+ x=94*2 (multiply 2 to both sides)
92.5+x=188
x=188-92.5 (subtract 92.5 from both sides)
x= 95.5 this is the score she need to make to avg 94%
2) you can draw a tree diagram. for example Flower1 branches off into 3 diff greens and then each of those greens branch off into 2 for with or with babies breath.
or you can simple multiply 4*3*2. you can do this because all choices are included with no restriction
your total number of options is 24
The answer is 169/5:8 = 5. It helps me alot it could help you to.